Agrochemicals including herbicides are used in the form of preparations such as emulsion, wettable powder, particle or granule, powder, flowable etc. For sufficiently bringing out the effect of raw agrochemicals, various measures have been made for physical properties of preparation forms, but under the present circumstances, further enhancement of the effect of agrochemicals by devising pharmaceutical forms is difficult. Because development of novel agrochemicals is further difficult, further enhancement of the activity of existing agrochemicals would be significantly meaningful in industry. For example, JP-A (W) 9-506615 discloses use of specific secondary or tertiary alcohol-based surfactants in order to improve rain resistance of herbicides such as glyphosate. JP-A 11-35406 (=WO99/03345) discloses that an alkylene oxide adduct of specific structure is used as an enhancer of the efficacy of various agrochemicals including herbicides.